Telephone system



TELEPHONE nsYsTEP/x 'Filed Nov. 2, 1933 Patented Jan. 28, 1936 TES PATENT GFFCE TELEPHONE SYSTEM Application November 2, 1933, Serial No. 696,333

8 Claims.

This invention relates to telephone systems and more particularly to' dial telephone systems.

The object of the invention is to provide an improved and economical trunking arrangement for dial systems in which the numbering system is such as to require the absorbing of a varying number of dialed digits.

According to one feature of this invention, a trunk circuit selectable through more than one level of a selector switch is provided with an auX- iliary switch operative in response to incoming impulses, and is arranged to further extend the connection after absorbing a varying number of digits dependent upon the level through which the trunk is seized.

A further feature of the invention is the arrangement of a digit absorbing trunk circuit to' render the further extension of the connection, after receipt of the required number of digits, dependent upon the continued closure of the calling line loo'p.

The drawing which forms a part of this specilication represents in schematic form a telephone system in which the features of this invention are incorporated.

Referring to the drawing, A represents a calling subscribers station; LF represents a linefinder having access to a group of lines including the line LI of station A; SI represents a rst selector permanently associated with the lineers station B. OT represents an outgoing trunk circuit connected to terminals in each of the third, eighth and tenth levels of the bank of selector SI and arranged for absorbing a variable number of digits depending upon the level through which it is seized. IT represents a jack ended incoming trunk circuit permanently connected over the trunk conductors i, 52 and 53 to the outgoing trunk circuit OT and also to a set of terminals in the tenth or O level of selector CD represents one of a group of common battery cord circuits common to the operators position at which the trunk IT terminates.

The subscribers numbers in this system are four, live and six digit numbers. Calls to lines having numbers comprising six digits are completed through the second level of the bank o'f the iirst selectors or other levels giving access to second selectors such as S2. Calls to lines having numbers comprising four digits are extended through the third level of the banks of the rst selectors to digit-absorbing trunks such as OT, the irst digit of these numbers being 3. Calls to lines having numbers comprising five digits are extended through the eighth level of the banks of first selectors to the same digit-absorbing trunks, the first digit o'i these numbers being 8.

The equipment at station A is of the type usually employed in automatic telephone systems and includes a dial 5. The switches LF, SI, S2, S3, S6 and C may all be of the well-known step-by-step two-motion type. For a detailed description of the construction and operation of selector and connector switches of this type, reference may be had to pages 53 to 65, inclusive of the 2nd edition of Automatic Telephony by Smith and Campbell published in 1921. The line-under may be similar to' that described in the patent to H. Hovland 1,711,682, granted May 7, 1929. Each of the selector and connector switches is represented in the drawing by a set of brushes and one or more sets of terminals, all of the operating magnets and associated relay equipment being omitted.

'Ihe outgoing trunk circuit OT includes the line relay 3I, release relay 32, auxiliary relays 33 and 34, and a rotary step-by-step switch DA comprising the stepping magnet 40, brush 4I and associated bank of terminals, the release magnet l2 and the off-normal contacts 43. The trunk circuit is connected to terminals I5, I6 and I'I in the third level of selector SI, to terminals I8, I 9 and 2d in the eighth level, and to terminals E I, 22 and 23 in the tenth level. The trunk circuit OT also includes a relay 35 associated with the terminals I5, iS and Il and a relay 45 associated with the terminals I8, I9 and 20.

The incoming trunk circuit IT comprises the line relay SI, release relay 62, sleeve relay 64 and an auxiliary relay 53 and terminates at the jack 'ifi of an operators position which is represented by the cord. CD.

Upon origination of a call at station A the line LI is extended by the operation of a linender such as LF to an associated first selector Si. In response to the dialing oi the first digit of a called subscriber-s number, the connection is further extended by the operation of the rst selector Si through its brushes il, i2 and I3 and an idle set of terminals in the level corresponding to the digit dialed. If the terminals in the selected level are connected to second selectors, the dialing of the remaining digits of the called number causes the selective extension of the connection through second, third and fourth selectors and a connector switch to the line of the called subscriber. To illustrate such a connec tion, the terminalsV I4 representing the second level of the bank of selector SI are shown connected to the second selector S2. The third and Vfourth selectors and the connector through which Vsuch a call is completed are representedV by S3, S4

and C; the called line and station are represented by L2 and B. A

If the digit dialed is 3, the brushes II, I2 and I3 are advanced into engagement with an idle Set of terminals in the tenth level. nals 2l, 22 and 23 represent such a set, the connection from line LI being extended directly over trunk conductorsl 5I and 52 through the outerback contacts of relay 64 of the incoming trunk circuit IT, through the windings of line relay 6I to ground and battery. Relay 6I is thereby oper- Y Y ringing sign-al to the calling subscriber. Relay 33 also Yconnects'ground to the sleeve conductor Y When the answering plug of an operators cord such as CD is inserted in the jack III to answer the call, the relay 64 is operated, thereby disconnecting the windings of relay 6I from the conductors 5I and 52. Relay EI and G2 release, thereby extinguishing the lamp 65. i Relay 34 also closes a circuit for holding relay 33 until the plug 'Il is removed from jack lll. Talking current is supplied to the callingrstation from the operators cordrCD.kk When the calling subscriber replaces the receiver on the receiver hook and the operator removes the plug 'II from jack 1G, the successive release of relays 34'Y and 63'disconnects the holding ground from conductor 53, thereby causing the return of switches SI and LF to normal in the usual manner. Y

If the iirst digit dialed is 3, the brushes II, I2 and I3 of selector SI are advanced into engagement with an idle set of terminals in the third level. The terminals I5,v I3 and II represent such a set, the connection from line LI being,'in this case, extended through the left inner and right back contacts of relay 35, through the inner back contacts of relay 34, and through the windings of line relay 3ly ofthe outgoing trunk circuit OT to ground and battery.V VThe operation f of relay 3l closes an obvious circuit for operating relay 32; and relay 32 connects ground through its right front contact over sleeve conductor'39 to terminal I'I to hold the selector SI and linefinder LF in well-known manner. 'I'he rst digit having been 3, the number is a four digit number and it is necessary to absorb the last three digits. When the second digit is dialed by the calling subscriber, the line relay 3l releases and reoperates in response to each of the Vdial impulses thus created. The release of relay 3I inresponse to the first impulse of the traincloses a circuit for operating relay33, this circuit being traced from Y' battery through the winding of relay 33, through Ythe outer left front contact of relay 32 to ground at the back contact of relay 3|. Being slow Yin releasing, relay 32 does not release during the receipt of impulses by relay 3|. Relay 33' is also slow to release and remains operated until after the'last impulse of a train has been received.

Theoperation of relay 33 closes a circuit from*V The termi-j battery through the winding of stepping magnet 4B of switch DA, in parallel with the resistance44, through the iront contact of relay 33 and inner left front contact of relay 32, to ground at the middle right back contact of relay 3d.Y When relay 33 releases, after all of the impulses created by the dialing of the second digit have been received, magnet dil releases.

Y relays3I and 33 and magnet 4B operate in like manner to advance the brush 4I into engage- The oper-ation Vof magnet lo advances the brush 4Ifrom normal ment with the second ofi-normal terminal;y the e dialing of the fourth digit causes the advance of brush 4I into engagement with the third Yoinormal terminal of its bank. The release of relay 33 after all of the impulses corresponding to the fourth and last digit have been received closes a circuit from battery through the winding and Y outer left back contact of rel-ay 35, third offnormal terminal and brush ll of switch DA,back

Y Contact of relay 33, conductor 38, back Vcontact or the continuity springs of relay 3d, and over conductor 39 to ground at release relay r32. Re-

lay 35 locks through its inner right front contact, over conductors 33 and 39 to the same ground. The operation of rel-ay 35 disconnectsthe windings of relay 3l from the line LI and closes a circuit from battery through the winding of relay 3d, outer right front contact 'of relay 35 through terminal I5 and brush I2 of selector Si, brush of line-finder LF', over line LI and through the telephone at station A, back through brush ,l of line-finder LF, brush II and terminal I5 of selector SI, and through the left'front contact of rel-ay 35 to ground. Relay 34 is thereby operated unless thejcalling subscriber has replaced the receiver on the receiver hook immediately after dialing the fourth digit. Relay 34 closes a locking circuit through the front contact of its continuity springs to ground attheeright front contact of relay 32.

With relay 34 operated, relay 35 releases whereby the connection from line LI is extended from terminals I5 and I6, through the left inner and right back contacts of relay 35, the inner front contacts of relay 34, over trunlcconductors 5I and 52, through the outer back contacts of relay 64 of the incoming trunk circuit IT, to the windings of the line relay 3l. The operation of relay 5I causes the connection of a holding ground to sleeve conductor 53 and the lighting of the answeringV lamp 65 as hereinbefore described.

The release of relay 3 I, due to the operation of relay 35 and the subsequent operation of relay 33, opens the circuit for energizing relay 32,Y but relay 3.2 is slow in releasing so that holding ground is connected to `conductor 53 in the incoming trunk vcircuit IT before relay 32 disconnects ground from conductor 39. The switching relay 34 is, therefore, held operated under'the control of release relay 62 of the incoming trunk circuit IT until the operator answers the .call and isthereater held operated under the control of relays 63 and 64 until the connection is released by the operator. The release of relay 32, upon extension of the connection to the incoming trunkl'circuitIT or upon failure of relay 34 to operate'rdue to the 'abandonment of the call by the calling subscriber,

closes a circuit from battery through the winding of release magnet d2 ofV switch DA, upperY contact of the oit-'normal springs 43, through the back contact of relay 32, to ground at the back contact of relay 3l. Theoperation of magnet 42 restores the brush 4I of switch DA to normal at which time the circuit through the winding of magnet 42 is opened at the off-normal springs 43.

If the rst digit dialed is 8, the brushes H, I2 and I3 of selector SI are advanced into engagement with an idle set of terminals in the eighth level. The terminals I8, I9 and 20 represent such a set of terminals, the connection from line LI being, in this case, extended through the left inner and right back contacts of relay 45, thence through the inner back contacts of relay 34, and through the windings of line relay 3I of the outgoing trunk circuit OT to ground and battery. Relay 3l operates closing the circuit for operating relay 32. The rst digit of the called number being 8, the number is a ve digit number and it is necessary to absorb four digits. The switch DA is thus advanced one step in response to the `impulse for each of the last four digits dialed.

When the brush 4I engages the third oir-normal terminal at the end of the impulses created by the dialing of the fourth digit, relay 35 operates as hereinbefore described, but relay 34 cannot operate since in this case the brushes II and I2 of selector SI are in contact with terminals I8 and I9 instead of terminals I5 and I6 so that the calling line LI is connected to the windings of line relay 3i through the contacts of relay 45 and not through the contacts of relay 35. As soon as the fourth and last digit is dialed, the operation of relay 33 and advance of brush 4I from the third ofi-normal terminal causes the release of relay 35, and when relay 33 releases after the last impulse a circuit is closed through brush 4I and the i, fourth oir-normal terminal for operating relay 45. Relay 45 locks through its inner right front contact and the back contact of the continuity springs of relay 34 to the holding ground on conductor 3S. The operation of relay 45 disconnects the windings of relay 3| from the line LI and closes a circuit from battery through the winding of relay 34, outer right front contact of relay 45, through terminal I9 and brush I2 of selector SI brush 8 of line-finder LF, over line LI and through the telephone at station A, back through brush l of line-finder LF, brush II and terminal i8 of selector Si, and through the left front contactl of relay 45 to ground. Relay 34 is thereby operated to release relay 45 and thus extend the connection from line LI to the line relay El of the incoming trunk circuit II'. The answering lamp lights, the call is answered and the switch DA is returned to normal as hereinbefore described.

Should it be necessary to absorb a diierent number of digits, another relay similar to relays 35 and i5 would be provided, there being one such relay for each of the diierent number of digits which it is necessary to absorb. It is of course understood that the invention is not limited to the particular arrangement shown in the drawing, and that the arrangement might be such as to absorb any one of a plurality of different number of digits when the digit absorbing trunk circuit is seized through a particular level or any one of a plurality of particular levels.

What is claimed is:

l. In a telephone system, a trunk circuit, a plurality oi branches incoming to said trunk circuit, trunk conductors outgoing from said trunk circuit, means for seizing said trunk circuit over any one of said plurality oi incoming branches, impulse receiving means in said trunk circuit, switching means for connecting said incoming branches to said outgoing conductors, and means for rendering said switching means operatively eiective after a required plurality of series of impulses have been received, the required plurality of series or impulses varying in accordance with the particular branch over which said trunk circuit is seized.

2. In telephone system, a digit absorbing trunk circuit, a plurality of paths over which said trunk circuit may be seized for use, a rotary switch, means for advancing said switch in response to the receipt of impulses corresponding to the digits to be absorbed, one step for each digit, an outgoing trunk line, and means operative in varying positions of said switch for extending the path over which said trunk circuit is seized to said outgoing trunk line.

3. In a. telephone system, a calling line, an impulse sender for said line, a digit absorbing trunk circuit, means for extending said calling line to said trunk circuit, an outgoing trunk, switching means rendered operative in response to the receipt of impulses corresponding to a certain number of digits for further extending said line to said outgoing trunk, and a circuit including the calling line for operating said switching means.

4. In a telephone system, a line, an impulse sender for said line, a selector comprising a set of wipers and a plurality of groups of terminals, means for connecting said line to said selector, a trunk circuit connected to terminals in a plurality of said groups, means responsive to a series of impulses created by the operation of said sender for operating said selector to seize the terminals of said trunk circuit in the group corresponding to the number of impulses in said series, means associated with said trunk circuit for receiving trains of impulses created by the operation of said sender, a switch, means for advancing said switch one step for each train of impulses incoming to said trunk circuit, outgoing trunk conductors, and switching means for extending the connection from said line to said conductors, said switching means being rendered operatively effective in a plurality of off-normal positions of said switch, the particular position in which said switching means is rendered eiective depending upon the particular one of said groups of selector terminals through which said trunk circuit is seized.

5. In a telephone system, a line, means for transmitting current impulses over said line, a selector comprising a set of wipers and a bank of terminals, the terminals being arranged in groups, means for connecting said line to said selector, a trunk circuit connected to terminals in a plurality of said groups, means responsive to a series of impulses created by the operation of said impulse sender for operating said selector to seize the terminals of said trunk circuit in a group corresponding to the number of impulses in said series, outgoing trunk conductors, and switching means in said trunk circuit operative in response to the receipt of a varying plurality of series of impulses from said sender for extending the connection from said line to said trunk conductors, the required plurality of series of impulses being dependent upon the particular group of selector terminals through which said trunk circuit is seized.

6. In a telephone system, a calling line, an impulse sender for said line, a trunk, impulse receiving means individual to said trunk, means for connecting said line with said impulse receiving means, a register controlled by said impulse re- Vceiving means to register the' number of series to the conductors of said trunk, and a` circuit,

controlled by said register and including said calling line for operating said electromagnetic means.

, 7. In a telephone system, a calling line, an impulse sender for said line, a trunk, impulse receiving means individual to said trunk, means for connecting said line with said impulse receivingmeans, a rotary switch controlled by said impulse receiving means to register the number of series ci impulses received, a test relay, and

rmeans rendered effective Vwhen the register switch is set in a particular position for disconnecting the calling line from said impulse receiving means and for connecting said line to the winding of said test relay the operation ci said test relay being effective to extend the connection from said line to the conductors of ,said trunk.

Y 8. In a'telephone system, a calling line, an impuls'efsender for saidrline, a trunk, impulse receiving means for said trunk, a selector comprising a set of Wipers and a plurality of groups of terminals, said impulse receiving means being connectedr to terminals in a pluralityfof said groups, means for connecting said line Yto said selector, means responsive to a series of impulses created by the operation of saidimpulse sender for operating said selector to extendthe calling Y line through the terminals in the group corresponding to the number of impulses in said series to said impulse receiving means, a rotary switch controlled by said impulse receiving means for registering th'e number of series of impulses received, a switching relay for use in extending the connection from said calling line through the terminals in any one of said groups to the conductors of said trunk, other relays, each of said of any one of said other relays. y Y

J Om E. CRUICKSHANK. 

